A FlowLayout arranges widgets from left to right until
there's no more space left. Then it begins a row lower and moves
from left to right again. Each component in a
FlowLayout gets as much space as it needs and no more. A
FlowLayout is useful for laying out buttons but not
for much else. This is the default LayoutManager for
applets and panels (special containers to aid with layouts about
which you'll learn more very shortly).
A BorderLayout organizes an applet into North,
South, East, West and Center sections. North, South, East and West
are the rectangular edges of the applet. They're continually
resized to fit the sizes of the widgets included in them. Center is
whatever's left over in the middle.
A CardLayout breaks the applet into a deck of
cards, each of which has its own LayoutManager. Only
one card appears on the screen at a time. The user flips between
cards, each of which shows a different set of components. The
common analogy is with HyperCard on the Mac and Toolbook on
Windows. In Java this might be used for a series of data input
screens, where more input is needed than can comfortably be fit on
one screen.
A GridLayout divides an applet into a specified
number of rows and columns which form a grid of cells, each equally
sized and spaced. As components are added to the layout, they are
placed in the cells, starting at the upper left hand corner and
moving to the right and down the page. Each component is sized to
fit into its cell. This layout manager tends to squeeze and stretch components
unnecessarily. However the GridLayout is great for
arranging Panels.
GridBagLayout is the most precise of the five AWT
LayoutManagers. It's similar to the GridLayout, but
components do not need to be the same size. Each component can
occupy one or more cells of the layout. Furthermore components are
not necessarily placed in the cells beginning at the upper
left-hand corner and moving to the right and down.
BoxLayout ????.
In simple applets with just a few components you often need only one layout manager. In more complicated applets, however, you'll often split your applet into panels, lay out the panels according to a layout manager, and give each panel its own layout manager that arranges the components inside it.